All the rotary motors and drives ever manufactured and used in industry, produce a torque which conforms the third Newton's law (action & reaction law) and as a result of the resistance of the load to rotation, the reaction of the produces torque is equally imposed to their shell and support in an opposite direction.
As a result, all electro motors and rotary drives should be fixed to a foundation or fixed support in order to pass the load reaction to the earth or a fixed place and to be capable to work. Otherwise, the produced power and torque of the motor will be applied to the shell of the motor and instead of rotating the output shaft, the shell of the motor rotates in an opposite direction.
Therefore, a rotary motors and drives not needing a fixed support such as earth would be advantageous.